This is a 6 month study evaluating the safety, pharacokinetics and efficacy of BXT-51072 in patients with mild to moderately active ulcerative colitis. The study will be conducted in two phases with the pharmacokinetic phase utilizing the resources of the GCRC. During the first week on study medication, patients will be hospitalized in the GCRC unit for days 1 and 2 and for 8 hours on day 7 when multiple blood samples will be taken to obtain information on the pharmacokinetics of BXT-51072 in patients with ulcerative colitis.